Cordelia's Siren Cipher

You focus on a piece of information that you want to encode and you choose a melody to decode the cipher. The information can be in a physical medium or in the memory of a willing creature. You can encode 1000 words, 1 image, or 1 minute of sound. Any ciphered text looks blurred and unreadable, images are obscured, sounds are distant and fuzzy. If the information is in memory, the remembering creature remembers it in the same way an outside observer would. 

If dispel magic or a similar effect is cast to dispel this effect, the information is destroyed and cannot be recovered. The spell ends when the code melody is played or sung nearby.